Liquid crystal (LC), light emitting diode (LED) and plastic optical fibre (POF) technologies are combined in a unique way to form full colour displays. Remarkable progress in LED technology has recently enabled high efficiency red, green and blue light sources with lifetimes of 100,000 hours. These are in current use for very large outdoor video displays (diagonal size of 20 ft, for example) with pixel spacings >2 cm, where the high cost of assembling from ˜100,000 to ˜1,000,000 LEDs is warranted. (Cost from $50,000 to $1,000,000 or more.)
In many applications, this is not affordable, particularly where a large number of pixels is desired. One approach is to use a bright white light source and then to use a LCD (liquid crystal display) light modulator to control the brightness of each pixel. This approach has a lower cost structure and has been demonstrated:
The publication “Case Study: Building the Market for a Tiled-Display Solution”, Needham, B., Information Display 10, pages 20-24, 2003, discloses an optical fiber-based display technology and application in public information displays and advertising.
A major issue with this approach is the loss of light associated with the LCD device. Typically only 5% of the light is used, and the remaining 95% is absorbed by components of the LCD.
Another issue is the strict requirement for exact alignment of the LCD units where an array of LCD units is tiled together to produce the desired display size. This generally requires that the image size of each LCD unit be expanded, allowing seamless tiling of the LCD units.
The publication “Psychophysical Requirements for Seamless Tiled Large-Screen Displays” Alphonse G A; Lubin J., Society for Information Display (SID) Digest, 49.1, pages 941-944, 1992, discusses the optical requirements of a tiled display system to achieve a seamless appearance to the human observer. The publication entitled “Optical Tiled AMLCD for Very Large Display Applications”, Abileah A; Yaniv Z, Society for Information Display (SID) Digest, 49.2, pages 945-949, 1992, describes an optical fiber module that may be used to enlarge the image size of a LC display enabling a tiled display.
The largest single light absorbing component of the LCD device is the colour filter array, used to separate the white light source into colour components. Typically, about 75% of the white light is absorbed by colour filters.
Other related references of general relevance include:
WO/03/067318 discloses a Tiled Display with Filter for Uniform Pixel Brightness which comprises an image display device having an array of electrically driven picture elements which are viewable at a viewing surface. Luminance corrections are arranged with respect to the image display device so as to apply a spatial luminance filter to the output of the image display device, the spatial luminance filter attenuating the light output by each picture element of the image display device in substantially inverse relation to the luminance response characteristics of the picture element so that each picture element exhibits substantially the same luminance for a given input electrical driving signal.
WO/03/067563 discloses a Display with Optical Fibre Face Plate which comprises an array of pixel elements; and an image guide having an array of light transmission guides, input ends of the light transmission guides being arranged to receive light from pixel elements of the image display device. Output ends of the light transmission guides provide an image output surface. Each light transmission guide includes a light-guiding region to promote light propagation by total internal reflection and a reflective coating on the light guiding region to promote specular reflection at the region-coating interface.
Therefore, it would be very advantageous to provide a tiled optical fiber display device structure in which the image size of a LCD display is expanded, enabling any desired number of LCD displays to be tiled together without gaps between them, so as to create a seamless picture, with superior display brightness and colour quality achieved due to backlighting with LED lamps and eliminating the need for light absorbing colour filters.